An automated feed table is often employed to feed bar stock and other types of workpieces to a machine tool, such as a band saw, table saw, drill or milling machine, etc. FIGS. 1 and 2 illustrate a prior art feed table apparatus 10a of the type used to feed small to moderate size workpieces to a band saw. Feed table 10a includes a roller assembly 11a which provides rolling support of a workpiece 12a (shown in phantom lines). The feed table also includes a fixed vise assembly 13a mounted to a feed table frame 15a and a movable shuttle vise assembly 14a movably mounted to feed table frame 15a. Fixed vise assembly 13a and shuttle vise assembly 14a cooperate to grip and stabilize workpiece 12a during cutting by machine tool 16a. Shuttle vise 14a also cooperate with the fixed vise to move the workpieces toward band saw 16a.
When production cutting of bar stock is performed, the feeding and cutting sequence typically includes the following automated steps: gripping of the bar or bars (workpiece 12a) with movable shuttle vise assembly 14a; releasing the fixed vise assembly 13a; advancing workpiece 12a toward the band saw and beyond blade 17a (which is moved to a retracted position) by moving shuttle vise assembly 14a; stabilizing workpiece 12a relative blade 17a by clamping the same by fixed vise assembly 13a; cutting workpiece 12a to length by blade 17a; releasing movable shuttle vise assembly 14a and moving it back away from cutting blade 17a while continuing to clamp workpiece 12a by fixed vise assembly 13a (and while retracting blade 17a); gripping workpiece 12a with movable shuttle vise assembly 14a; releasing fixed vise assembly 13a; and advancing workpiece 12a back toward cutting blade 17a for another cut.
Additionally, a fixed vise (not shown) will usually be provided on the saw table or base 19a to grip the workpiece immediately proximate blade 17a. Such a saw table vise also is automatically operated to open and close with operation oil the feed table vises (usually substantially in the same operation mode as fixed vise 13a).
Feed table designs, such as that illustrated in FIGS. 1 and 2, generally include opposing vise jaws 18a and 18a' cantilevered upwardly from vise bases 20a and 20a' which are mounted (or movably mounted, with respect to shuttle vise 14a) to feed table guide ways 15a. Upward cantilevered jaws 18a and 18a' have been found to have a common problem; namely, when clamping workpieces 12a, and particularly large workpieces, opposing jaws 18a and 18a' tend to spread apart or open up at the upper portions of the jaws. As jaws 18a and 18a' push against workpiece 12a, the resistance to compression exerted by workpiece 12a causes upper portions or ends of opposing jaws 18a and 18a' to separate outwardly.
Such separation can be problematic because workpiece 12a will not be properly gripped by either fixed vise assembly 13a and/or shuttle vise assembly 14a, which may permit workpiece 12a to move or slip upwardly and/or axially during the cutting sequence. Accordingly, workpiece 12a may be improperly cut, adversely affecting cutting precision and accuracy, and in extreme situations, necessitating scrapping of workpiece 12a or portions cut from the workpiece. Typical of such prior art feed table designs are the feed tables disclosed in U.S. Pat. No. 4,179,961 and U.S. Pat. No. 3,504,585 to Harris; and U.S. Pat. No. 3,474,693 to Wilkie et al.
As the length, diameter, and accordingly the weight, of workpieces increases, machine tool feed tables have employed roller assemblies which include a plurality of side-by-side rollers capable of supporting and advancing larger and heavier workpieces. Such prior art feed tables, as illustrated in FIG. 3, also typically include reaction frame assemblies 21b which add substantial lateral stability and rigidity to the opposing jaws of the fixed vise and/or shuttle vise assemblies.
In FIG. 3, such a prior art feed table is illustrated and can be seen to include a vise reaction frame assembly 21b which extend over (upper cross-beam 23b) and under (lower cross-beam 24b) a guide roller assembly 11b. The vise reaction frame is positioned to resist the tendency of the opposing vise jaws 18b and 18b' of shuttle vise assembly 14b to open up in reaction to the clamping of workpieces (not shown). Shuttle vise assembly 14b includes at least one movable jaw 18b mounted to a first upright post 22b and an opposite jaw 18b' which may be rigidly fixed to a second upright post 22b'. Reaction frame assembly 21b, therefore, includes cross-beams 23b and 24b which are rigidly secured between the top and bottom of first post 22b and second poser 22b' to encircle roller frame assembly 116. Accordingly, gripping of a workpiece is very positive since the reaction forces are resisted by reaction frame assembly 21b. This reduces the tendency of opposing jaws 18b and 18b' to spread apart during clamping of workpieces.
In order to provide for displacement or shuttling of vise 14b, vise reaction frame assembly 21b must be capable of shuttling longitudinally along roller assembly 11b. Thus, lower cross-beam 24b is typically mounted on a pair of drive screws 25b and 25b' which reciprocate shuttle vise assembly 14b relative to roller assembly 11b. In operation, therefore, drive screws 25b and 25b' cause reaction frame assembly 21b and vise jaws 18b and 18b' to shuttle along feed table apparatus 10b outside longitudinal roller assembly frame members 26b and 26b'. As will be seen from FIG. 3, however, this construction requires that roller assembly 11b be mounted by legs 28b at the ends of frame members 26b and 26b' to table base 15b so that the cross-beam members can pass above and below roller frame members 26b and 26b'.
Accordingly, although reaction frame assemblies of this type effectively counteract the reaction forces caused by clamping the workpiece with jaws 18b and 18b', they, require a long span of roller frame members 26b and 26b' between its support legs, and they include an upper cross-beam 23b, which prevents laying the bar stock directly on the feed table from above. Additionally, such prior art vise reaction frames are rather complex, bulky and costly to construct.